A technique in which a sensor sheet is provided in a control panel of an onboard audio device is described in, for example, Japanese Unexamined Patent Application Publication No. 2012-123449 (Patent Literature 1). In the technique described in the gazette, “a surface coating of gray, black, or the like is applied” (see paragraph [0013]) to the control panel, and in the control panel, “printing indicating the position and function of a switch” (see paragraph [0014]) is performed at a portion corresponding to the switch, such that the printing or the like distinguishes the switch portion and the other portions from each other. Furthermore, a touch panel substrate (a sensor sheet) is disposed inside the control panel in an adhered manner (see paragraph [0015]) such that a predetermined input can be performed through a touch operation.